1. Field of the Invention
The present invention relates to a hydraulic brake lever assembly, and more particularly to an oil guiding device for hydraulic brake lever assembly having a brake lever for preventing formation of air bubbles in hydraulic oil during operation.
2. Description of Related Art
The braking system of a bicycle is the key component for controlling speed of the bicycle and maintaining the safety for riding. A conventional hydraulic brake assembly for bicycle rim brake includes an oil tank for containing oil, a brake lever pivotally connecting to one end of the oil tank, and a tube for connecting with a caliper body is engaged to another end of the oil tank. When the brake lever is exerted, the oil stored in the oil tank is pressured into to the tube, thereby forcing the caliper body to push toward a rim until the rim is forced to brake. The hydraulic brake assembly is widely applied on various types of bicycles for the outstanding braking effect it can achieve.
In the conventional hydraulic brake assembly, the oil tank includes a chamber and an oil storage unit respectively formed in two laterals thereof The chamber is adapted for receiving a piston assembly which is slidably movable therein. The oil storage unit is adapted for storing oil which is provided for braking. A first guiding hole and a second guiding hole are defined between the chamber and the oil storage unit such that the chamber and the oil storage unit are communicated for the oil to flow therein between. The first guiding hole and the second guiding hole have different diameters. Thereby when a rider exerts the brake lever, the piston assembly pressured the oil in the chamber to the caliper body through the tube, when the rider releases the brake lever, the oil in the oil storage unit passes through the first guiding hole to the chamber such that oil in the chamber is maintained in a sufficient level for braking and preventing malfunction due to insufficient oil.
However, despite the effect it provides, the conventional hydraulic brake assembly has the following drawbacks. Usually the brake lever is downwardly and inclinedly positioned relative to the bicycle handlebar for gripping purpose such that the oil tank is also downwardly and inclinedly positioned relative to the bicycle handlebar. When the oil tank is inclinedly positioned, the oil in the chamber would flow into the caliper body through the tube, causing excessive oil to accumulate in the caliper body. In addition, due a tilted position of the oil tank, air may enter into the hydraulic oil through first and second guiding holes causing formation of air bubbles in the hydraulic oil, which results in a “spongy brake” operation and would influence the performance of the hydraulic brake assembly as hydraulic pressure can no longer be distributed accurately and may consequently lead to serious injuries of the rider.
The present invention has arisen to obviate/mitigate the disadvantages of the conventional hydraulic brake assembly.